Embodiments of the invention relate generally to electric drive systems including hybrid and electric vehicles and, more particularly, to transferring energy between one or more energy storage devices and multiple electromechanical devices of the vehicle using a multi-channel DC bus.
Purely electric vehicles use stored electrical energy to power an electric motor, which propels the vehicle and may also operate auxiliary drives. Purely electric vehicles may use one or more sources of stored electrical energy. For example, a first source of stored electrical energy may be used to provide longer-lasting energy while a second source of stored electrical energy may be used to provide higher-power energy for, for example, acceleration.
Hybrid electric vehicles may combine an internal combustion engine and an electric motor powered by an energy storage device, such as a traction battery, to propel the vehicle. Such a combination may increase overall fuel efficiency by enabling the combustion engine and the electric motor to each operate in respective ranges of increased efficiency. Electric motors, for example, may be efficient at accelerating from a standing start, while combustion engines may be efficient during sustained periods of constant engine operation, such as in highway driving. Having an electric motor to boost initial acceleration allows combustion engines in hybrid vehicles to be smaller and more fuel efficient.
While propulsion system configurations for purely electric vehicles and hybrid electric vehicles have been developed to include multiple sources of electrical energy to increase energy or power density and multiple power sources to achieve desired propulsive output, incorporating these energy storage and power sources into a propulsion system increases the overall size, weight, and cost of the system. Further, the limitations imposed by configuring a propulsion system to operate with multiple power sources in combination with one or more energy storage sources reduces the operating efficiency and fuel economy of the individual components of the propulsion system in addition to reducing the overall system efficiency.
Therefore, it would be desirable to provide an electric and/or hybrid electric propulsion system that incorporates multiple electromechanical devices and one or more energy storage systems in a manner that improves overall system efficiency and permits the individual components of the propulsion system to be operated independently to improve the individual operating efficiencies thereof.